JP3408636B2 - Image reading method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading method in an image measuring device having two or more systems of sensors using a CCD, and when reading data by the CCD, one system overflows and measurement is impossible. The present invention relates to an image reading method that can be avoided. 2. Description of the Related Art In recent years, image processing and measurement using a CCD have been used in many fields as computers have become faster, smaller and lighter. In particular, various satellites have been launched and are operating as space development progresses. In this satellite device, a small and high-speed computer and a CCD are combined, but image processing is being developed one after another. The present invention is particularly effective for image processing in satellite equipment.

[0002]

2. Description of the Related Art Needless to say, attitude control is particularly important in satellites. Conventionally, various kinds of attitude detection methods and control methods have been developed. In particular, a “star sensor” that performs attitude control based on a star is frequently used as a satellite attitude detector with high accuracy. By the way, in general, satellite attitude control has two sensors,
The attitude of the satellite is corrected using the data acquired from the two fields of view. This star sensor is usually linked with a computer and has a good reputation as an extremely high-precision attitude detector.

FIG. 3 is a processing flowchart of a star sensor used for satellite attitude control. The star sensor periodically sets an imaging condition and outputs an imaging instruction (ST1). At this time, the discrete level D1 (see FIG. 4) is set. When the image pickup is completed (ST2), the image pickup data from the CCD is stored by the hardware in the buffer only for the data of the discrete level or more on a line-by-line basis (S).
T3).

When the storage of data for one line by the hardware processing unit is completed, the software processing unit reads the data of the line and stores it in the table for image processing (ST4). As shown in FIG. 4, this process is switched by the switch SW and alternately performed in two systems, and the write instruction and the data read are alternately performed by software. Then, the computer calculates the center of gravity of the star based on the storage table of the image processing data (ST5) and outputs the calculation result (ST6).

Incidentally, steps ST1, ST4, ST5,
ST6 is a software process, and steps ST2 and S
T3 is a hardware process. Further, in steps ST3 and ST4 within the dotted line, software issues a hardware write instruction and a software read instruction to each other. By the way, in order to detect the attitude of the satellite, which changes from moment to moment, it is essential that the star sensor is always in a state capable of measuring both systems, or in a state capable of measuring at least one system. On the other hand, in a satellite-mounted computer, it is difficult to adopt a high-speed read clock, a large-capacity buffer memory, etc. due to restrictions such as ensuring reliability and weight limitation. In addition, since a processing system using multiple CPUs is currently difficult for an on-board computer, it is necessary to construct an efficient processing system using software.

FIG. 4 is an explanatory view of a processing procedure of conventional image pickup data. CCD-A and CCD-B are sensors, and two systems are prepared. The output of each CCD is A / D converted,
It is input to each level selector A, B. The level selectors A and B are selectors for extracting data of the discrete level (D1) or higher. In addition, the line buffers A and B
Is a buffer memory for storing data of discrete level or higher. The storage from the CCD detection to the line buffer is a processing by hardware.

First, the image pickup data, which is analog data for each line, is converted into digital data by the A / D converter for processing by the CPU, and then data having a discrete level or higher which is designated in advance by the level selector is converted. Only the data of the discrete level D1 or higher is extracted and stored in the line buffer. Here, the discrete level D1 of the level selector is calculated by the designated threshold level and the bias level calculated in the previous imaging.

The switch SW switches between the A and B systems, and stores the switched data in the storage table TB. Switching of the switch SW and storing are software processes. That is, when the storage of the data for one line is completed in the line buffer, the CPU stores the data in the buffer (table) for image processing. In this case, since these processes are performed for two systems, the same process is performed for another system after the processing for one line is completed, and the write instruction and the data are alternately written by the software by performing these processes alternately. Read.

[0009]

As described above, since the discrete level D1 set in the level selector is based on the bias level in the previous image pickup, it is not an appropriate value when the previous image pickup conditions are different. there is a possibility.
As a result, a large amount of data is stored in the buffer, and the subsequent processing becomes a burden.

Further, even if the above-mentioned condition occurs in only one system, the other system will be affected accordingly. In such a processing system, if the data of one system overflows, the processing of the other system cannot be performed in time, and there is a problem that the processing is not completed in both systems. For example, a star sensor, which is one of the satellite attitude determination systems, sees the sensor on one system side toward the earth due to its orbital relationship. May become bright and the data of that line may overflow.

In the conventional star sensor, when one system overflows and the processing is not completed, the operator recognizes this situation and sets the imaging conditions (imaging time, gain, threshold value) to cope with this situation. This was dealt with by sending a command to change or power off the system.
An object of the present invention is to improve a method of setting a discrete level and to detect a posture with higher accuracy, and to provide an image reading method by this setting method. That is, in the present invention, the setting of the new discrete level used for the level selector is set based on the bias level in the image pickup. In this case, the bias level is calculated from the data read a few lines before, and this value is calculated. By setting the data on the basis, the appropriate new discrete level is set. In addition, the sensor data when the entire surface of the sensor becomes brighter has a certain level of continuous data compared to the normal data, so the direction of the sensor is detected by detecting the continuity of the data from the sensor. Recognize whether you are pointing to or to the earth, and control the reading of data so that the processing is not completed.

[0012]

The present invention comprises at least two aspects.
Having a sensor of a system, selecting the imaged data by the sensor at a predetermined discrete level, storing the selected data in a line buffer, storing these in an imaged data storage table by switching these systems by switching means, and storing the data. An image reading method in an image measuring device for performing predetermined control based on image pickup data stored in a table, the level calculating means L being provided between a switching means SW and a storage table TB.
C is provided, the continuity of the imaging data is checked by this level calculation means, and the bias level of the line is calculated.
The new discrete level D2 is determined based on the bias level, the new discrete level is sent to the level selector, and the level selector selects the imaging data according to the new discrete level.

In this case, the new discrete level is calculated by using the bias level of the image data previously read several lines before the same image. In addition, when checking the continuity of the imaged data, the level calculation means determines that the data stored in the line buffer is abnormal data when the data is equal to or more than a predetermined number of data for one line in a row, and the system is determined by the switch SW. Stop the switching operation, stop the data reading of the system determined to be abnormal, and process only the system on the normal side.

Further, the sensor is used as a star sensor used for attitude control of a satellite. Further, the sensor, the level selector and the line buffer are processed by the hardware part, and the switch, the level calculating means and the storage table are processed by the software part.

[0015]

According to the present invention, first, as the set value of the discrete level, the bias level of the line read several lines before the same image pickup is used instead of the bias level calculated at the previous image pickup. When the discrete level D2 is set, and when the software processing unit reads the data stored in the line buffer, the continuity of the data is checked and whether the data is normal data or not is determined by the number of data for one line. If more than the continuous rate (%) of data is continuous on the line, it is judged as abnormal data, the switching operation of the system by the switch SW is stopped, and the reading of data of the system judged to be abnormal is interrupted. Only the other system on the normal side is processed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram of a processing procedure of image pickup data according to the present invention. Hardware processing unit sensor CCD, A /
The D converter, the level selector and the line buffer, the switch of the software processing unit, and the storage table are shown in FIG.
It is the same as the conventional configuration. As shown in the figure, in the present invention, the level calculating unit L that checks the continuity of data and calculates the bias level that is the basis of the discrete level determination.
C is provided inside the software processing unit.

In setting the discrete level D2, the level calculator of the present invention uses the previous bias level at the time of simultaneous image pickup for calculation. Therefore, even when the screen becomes bright as a whole, it is possible to set the discrete level D2 corresponding to the brightness. Furthermore, when reading data from the line buffer, the continuity of the data is checked, and if continuous data of a certain level exists over several lines, it is determined that stray light has entered the sensor and the entire surface of the sensor has become bright, The system data reading process is interrupted. Therefore, when the entire surface of the CCD of one system becomes bright, the reading of that system is stopped, and the other can be processed within the time limit.

In the star sensor processing flow chart of FIG. 3 described above, as a series of processing of the star sensor, the imaging instruction, the reading of the imaging data, the determination of the center of gravity of the star, and the output of the calculation result were performed, but these processings were determined. Must be done in time. However, writing the data to the line buffer in the hardware processing unit requires about 1/3 of the entire processing time, and further reading the data from the storage table in the software processing unit and determining the center of gravity of the star remain. Must be done in no time. In this way, depending on the processing time required to read data from the buffer,
It is determined whether or not the series of processing can be completed within the time. Therefore, according to the image reading method of the present invention, switching of the system is not performed even when an overflow occurs in one system, and the data reading of the system in which the overflow has occurred is interrupted. Also, it becomes possible to determine the center of gravity of a star within the processing time limit.

FIG. 2 is a processing flowchart in the level calculating section according to the present invention. As described above, the level calculator LC checks the continuity of data and calculates the bias level. Explaining the A system, as shown in FIG. 1, first, data of one line is read by the sensor CCD-A (ST11a), and the obtained analog data is converted into digital data by the A / D converter (ST12a). , Then only the data above the discrete level set in the level selector A is C
The address on the CD is added and stored in the line buffer A (ST13a). The description for the system B is omitted because it proceeds in parallel in the same manner.

Next, in the software processing section, the switch SW is changed over, and the level calculation section alternately reads the data from the line buffers A / B (ST14), checks the address, and checks 60% or more of the data for one line. If the data of No. is continuous, the reading of the data of that system is interrupted (ST15). Then, the bias level is calculated, and the result is sent to the level selector (ST1
6).

[0021]

As described above, according to the present invention,
Even if one sensor looks at the bright side of the earth, it has the effect of interrupting the processing of that system in the middle of reading and processing only the other system and reflecting the result in the attitude determination of the satellite. In the next image pickup, both systems give an instruction, and therefore, when the earth disappears from the field of view of the sensor, both systems can automatically return so as to perform processing.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a processing procedure of imaged data according to the present invention.

FIG. 2 is a processing flowchart in a level calculation unit according to the present invention.

FIG. 3 is a processing flowchart of a star sensor used for attitude control of a satellite.

FIG. 4 is an explanatory diagram of a processing procedure of conventional imaging data.

[Explanation of symbols]

SW ... switch LC: Level calculator TB ... Image processing data storage table D1, D2 ... Discrete level CCD-A, B ... Sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhisa Tanaka 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (56) Reference JP-A-60-60100 (JP, A) JP-A-3-51713 (JP, A) JP 63-175719 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 1/04-1/207 B64G 1/36 G01C 21/24

Claims (4)

(57) [Claims] 1. A has a sensor least <br/> also two systems use the attitude control of the satellite, Ta Ri by the said sensor of the satellite
The imaged imaged data is selected at a predetermined discrete level, the selected imaged data is stored in a temporary line buffer, and the two systems are switched by a switching means to store the imaged data in a storage table. In an image reading method in an image measuring device for controlling the attitude of an artificial satellite based on stored image pickup data, a level calculating means (LC) is provided between the switching means (SW) and the storage table (TB). , The image pickup data is at a predetermined level by the level calculation means.
It is checked whether the above is continuous , and the imaging data
When the level is not continuous for more than a predetermined level, the threshold level
And the imaging data stored in the storage table
Bias level calculated for, to determine the bias level as a new discrete level (D2), further sends a該新discrete level to level selector in said level selector selects the imaging data by該新discrete levels, An image reading method characterized by the above. 2. The image reading method according to claim 1, wherein the new discrete level is obtained by a bias level of image data previously read several lines before the same image is captured. 3. The level calculation means stores the image pickup data.
When checking whether or not the image data continues for a certain level or more, the image data is stored at a predetermined level when the image data stored in the line buffer is continuously equal to or more than the number of data for one line.
Determines that abnormal data as contiguous or Le, the switching
The switching operation of the two systems by the replacement means is stopped, the data reading of the system determined to be abnormal is interrupted, and the normal system is stopped.
The image reading method according to claim 1, wherein the data from the document is read and processed. 4. The image reading method according to claim 1, wherein the sensor is a star sensor used for attitude control of an artificial satellite.